Over forty years ago there was developed a method of transverse flux induction heating wherein induction heating coils were arranged in side-by-side relation transversely of a path of movement of sheet metal. These coils were arranged in pairs on opposite sides of the path of such moving sheet metal. This transverse flux induction heating had a number of deficiencies including the overheating of strip edges only. In transverse flux induction heating, little or no current flows under the slot area between adjacent coils while most of the current flow is under the poles of the coils. As the strip starts to move, the strip becomes a conductor flowing through a field and a second current flows. Due to the second current there is loading under the poles and no loading under the slots. In other words, the loading is pulsating. A pulse can be made up of a fundamental plus harmonics. The wider the strip, the lower the inductance at the edges of the strip. The harmonics generated will flow where there is a minimum inductance which is along the edges.
Further, with transverse flux heating of steel, there is up to 80% efficiency. Normal induction heating is only 40% efficient or less.
The biggest problems with using transverse flux induction heating have been:
1. The edges have overheated and must be sheared off as scrap. PA1 2. Overheating of the edges increase with strip speed. PA1 3. Prior transverse flux induction heating setups could only accommodate one strip width. PA1 4. The thickest slab that could be heated was less than 1/2 inch.